This invention relates to an improvement of prestressed concrete piles, poles or the like pillers and particularly to providing the prestressed concrete piles, poles or the like pillers covered with an outer shell of a steel pipe on a circumferential surface of a cylinderical prestressed concrete tube or a piller shaped prestressed concrete pole which is a main part of the said prestressed concrete piles, poles or the like pillers so as to act a force upon the said piles, poles or the like pillers independently of the said concrete tube or pole, when force is given to the said piles, poles or the like pillers.
One of the objects of this invention is to provide prestressed concrete piles, poles or the like pillers in which compression force applied to the pillers acts on the tubular body of concrete itself whereas, bending moments of the prestressed concrete piles, etc. mainly works on the tubular steel plate covering the outer surface of the tubular concrete body. Another object of this invention is to provide the prestressed concrete piles, poles or the like pillers having a small frictional surface resistance same to that of the steel pipe when the said prestressed concrete piles, poles or the like pillers are pounded into the ground as fundamental piles.
Another object of this invention is to provide the prestressed concrete piles, poles or the like pillers having the increased compressive strength of the said prestressed concrete tube or pole preventing the generation of lateral stress within the said concrete tube or pole in a radial direction by providing the outer shell of the steel pipe on the circumferential surface of the said concrete tube or pole.
The further object of this invention is to provide prestressed concrete piles, poles or the like pillers having a larger bending resistance by arranging plural axial reinforcing steel wires suffering the bending stress nearer to the circumference of the concrete tube or pole than those of the prior prestressed concrete piles, poles or the like pillers.